<template>
    <div class="nav-bar" :class="{ 'is_fixed': isFixed }">
        <div class="container">
            <div class="pro-title">
                {{title}}
            </div>
            <div class="pro-param">
                <a href="javascript:;">概述</a><span>|</span>
                <a href="javascript:;">参数</a><span>|</span>
                <a href="javascript:;">用户评价</a>
                <slot name="buy"></slot>
            </div>
        </div>
    </div>
</template>
<script>
    export default {
        name: 'nav-bar',
        props: {
            title: String,
        },
        data(){
            return {
                isFixed: false,
            }
        },
        mounted(){
            // 注册事件
            window.addEventListener('scroll',this.initHeight);
        },
        methods:{
            initHeight(){
                // 页面 Y 轴偏移量 兼容 IE
                let scrollTop = window.pageYOffset ||           document.scrollTop || document.body.scrollTop;
                this.isFixed = scrollTop > 152 ? true : false;
            }
        },
        destroyed(){
            // 通过第三个参数设置 事件冒泡 来销毁事件
            window.removeEventListener('scroll',this.initHeight,false);
        }
    }
</script>
<style lang="scss">
    @import './../assets/scss/config.scss';
    @import './../assets/scss/mixin.scss';
    .nav-bar{
        height: 70px;
        line-height: 70px;
        border-top: 1px solid $colorH;
        background-color: $colorG;
        box-shadow: 0 5px 5px $colorE;
        z-index: 10;
        &.is_fixed{
            position: fixed;
            top: 0;
            width: 100%;
        }
        .container{
            @include flex();
            .pro-title{
                font-size: $fontH;
                color: $colorB;
                font-weight: bold;
            }
            .pro-param{
                font-size: $fontJ;
                span{
                    margin: 0 10px;
                }
                a{
                    color: $colorC;
                }
            }
        }
    }
</style>